Optical discs, such as compact discs (CDs) and digital versatile discs (DVDs), are a form of computer-readable media that provide storage for digital information. Some optical discs may be read-only, while others may also be written to. Typically, one side of an optical disc is referred to as a data side, while the other side is referred to as a label side. The label side may include label text and/or graphics.
An optical disc drive is used to read from and, in some cases, to write to the data side of an optical disc. An optical pickup unit is included in the optical disc drive and is configured with a laser and sensors for reading from and writing to the data side. An optical pickup unit may also be configured for writing to the label side. However, writing to the label side may involve using a larger laser spot size to write on the label side than on the data side because the tracks written to the label side are generally wider than are commonly written on the data side. Therefore, writing to the label side often involves defocusing the laser spot to make it larger. One problem that may occur with this is controlling the defocusing so as to optimally adjust the spot size.